2-cycle gasoline engine of the fuel injection type



A. LENNING Nov. 16, 1954 2CYCLE GASOLINE ENGINE OF THE FUEL INJECTION TYPE Filed July 29, 1952 m M W /4 /l/ar United States Patent G 2-CYCLE GASOLNE ENGINE 0F THEFUEL INJECTIN TYPE Alvar leuning, Stockholm, Sweden, assigner to AB. Kaba, Stockholm, Sweden, a corporation of Sweden Application July 29, 1952, Serial No. 301,492

4 Claims. (Cl, 123--29) My invention has for its object a novel system for injecting volatile fuel into the crank case of 2-cycle combustion engines of the type where the air admission into the crank case is governed by a valve. More particularly said fuel injection takes place through an aperture in the air admission valve disk, and is synchronized with the valve action. Other features will be apparent from the following specification.

The customary method for supplying a 2-cycle combustion engine with volatile fuel consists in using a carburetter in which fuel is dispersed into the combustion air. Such carburetters are usually provided with a iloat Valve to maintain the desired fuel level in relation to the dispersion nozzles and are therefore inadequate in cases where the engine is to be operated in different angular positions in reference to a horizontal plane (e. g. for operating lumber saws, chisel machinery etc.). The direct injection principle as used in certain air craft equipment, is not readily applicable in small 2-cycle engines owing to its intricacy. Another shortcoming of the conventional carburettor consists in its lack of ability to hold down the engine speed when full engine load suddenly falls olf. The present invention has for its object to solve these problems simultaneously, and in a simple and inexpensive way.

The invention is presently to be described in conjunction with the accompanying drawing in which Fig. l is a horizontal section view of an air regulating and fuel injection apparatus according to the invention and applicable to a single cylinder engine having a vertical crank shaft. Fig. 2 represents an end view of the apparatus shown in Fig. l; Fig. 3 shows an extract from Fig. l, specifically a fuel pump and an air intake valve, although in a different operational position.

In Fig. l reference number 1 indicates a section through the vertical crank shaft; 2 is a cam, integral with said shaft and adapted to operate the combined air valve and fuel pump. An intermediate lever 3 serves to convey the cam motion by means of a push rod 4 to an air valve disk 5 having a stem 6. Said stem is provided with an axial channel 7 which continues through the valve disk and emerges at 8 on the crank case face of the valve disk. The air valve is actuated in a closing direction by means of a helical Valve spring 10.

The valve stem 6 is guided by an essentially cylindrical pump sleeve 11. Its valve stem bore is in the left portion widened to a slightly larger diameter for the accommodation of a differential piston 12, having an axial channel. A spring 13 keeps the differential piston pressed against the butt of the valve stem 6. At one side the pump sleeve 11 is provided with a supply aperture 15 for the fuel to be injected. It should be observed that an annular space 14 will form around the extreme end of the valve stem where it emerges into the widened bore portion.

The pump sleeve 11 is axially movable in a cylindrical body 16 which is attached to the engine crank case by means of a flange 17. The `axial movement of sleeve 11 is limited in both directions: to the right by means of a stop member 18 which surrounds the fuel inlet conduit and is carried through a slot in the body 16. To the left the sleeve butts against a setting disk 21 at a place designated by 19. The setting disk is rotatably connected to the body 16 by means of a comparatively coarse thread 20. It is furthermore secured to a regulating knob 22 by means of a screw 23, permitting the setting disk to be set and locked by friction at a variety of angles.

The :regulating knob V22 is integral with =an external sleeve 24 which carries va cylindrical air intake flter 25 made of wire mesh. On Jthe inside of the air lter there is provided in the external sleevelan air aperture 26 which cooperates with a 'V-shaped slot in the stationary body 16. A friction :providing spring 28 serves to keep the combined .knob 22 and sleeve 24 in any set position. A plug 29 which closes oif the pump sleeve llat its extreme end is shaped as a push button, accessible from the left.

In Figures 2 and 3 ythesame designations as in Fig. l are employed to designatethe same parts.

The apparatus works as follows: When the engine shaft 1 rotates it causes the cam 2te actuate the air valve S'by the intermediary of members 3and -4. It will be assumed that the cam is so situated on the shaft that valve 5 vis being opened in thefcorrect operational phase, i. e. during the crank case suction period. Air will then be drawn into the crank case and maybe regulated by turning 'the k-nob .22, i. e. by changing the setting of aperture 26 .in relation to the V-slot 27.

Simultaneous with the 'air influx 4a certain quantity of fuel will be injected into the crank case through channel 8 in the valve disk 5. For explaining this action more in detail reference is made vto Fig. 3 which shows the valve stem 6 in a depressed position relative to the pump sleeve 11.

It should be apparentthat such part of the fuelwhich a moment earlier was'situated'rto the leftiof the differential piston 112 will have been displaced into the channel'7 and into .the engine. .At this pump stroke the aperture 15 in the pump sleeve hasbeenlaid bare, causing new fue] to be drawn in rapidly into the annular space 14, since lthis space grows as the valve stem performs its leftward motion (compare the size of the annular space in Fig. 1). When the valve stem commences its motion towards the right the aperture 15 will gradually close; during this phase part of the fuel in the annular space returns through aperture 15. When aperture 15 has been closed off entirely an overpressure-determined by the spring 13-will be created in the annular space. This pressure brings the differential piston to a moments stop, creating a break in the mechanical contact between the differential piston and the valve stem 6. As a consequence part of the fuel enclosed in the annular space will find its way into the channel in the differential piston and into the suction space to the left of it. Some of the fuel which is situated in the valve stem channel will also return towards the left through the differential piston channel. This is obvious from the fact that that part of the stroke (of the stem end) which takes place over and to the left of aperture 15 will not produce any injection.

Thus the fuel quantity injected per stroke will be relatively small when the pump sleeve 11 is set closer to the crank case, and attains a maximum when the sleeve is set so far towards the left that the aperture 15 is laid bare only during a small portion of the operational amplitude. Changing the pump sleeve setting, and consequently the rate of pumping, is effected by the knob member 22, 24, i. e. by the same member which throttles the air. The correct ratio between fuel and air is first to be determined experimentally by properly shaping the V-slot 27 to correspond to the pitch of the thread 20. When the engine is running at a higher speed this ratio will not change appreciably if the volumetric efficiency of the pump tends to drop approximately as the volumetric eicency of the engine itself.

Other experiments have substantiated a theory that the device according to the invention will serve also as an automatic speed limiter. By choosing a proper relation between the mass of the differential piston and the force exerted by the spring 13 there will be established a critical engine speed above which the differential piston will no longer closely follow the motion of the valve stem 6. When such is the case the device ceases to pump (or the delivery will be materially reduced), thus obviating runaway conditions. It has been ascertained that the maxi mum speed thus controlled need not be higher than around of the normal top performance speed of the engine, not even when the air intake is left wide open.

lt remains to describe the function and purpose of the setting disk 21, the push button 29, the aperture 9, and the stop member 18. The setting disk21 transmits the motion from the knob 22 to the thread 20. By setting the disk 21 differently, by overcoming the friction from screw 23, the ratio between fuel and air will be changed to accommodate the engine to variations in fuel quality and in operating temperatur The push button 29 serves the purpose of priming the engine. If the button is depressed while the engine is at a standstill the pump will perform a stroke. If it is depressed to the extent that the aperture 9 is laid bare by the annular space 14, the fuel will flow directly into the crank case, if the fuel head so permits. It should be noted that the fuel pumping device is well suited to work in conjunction with a fuel tank under artificial pressure, at least if it is made with reasonable precision. The stop member 18, which is provided with an integral excenter, serves as an adjustable stop when turning the knob 22 towards the idling or low speed position.

The device now having been described may be varied in several ways and still remain within the scope of the invention. It is e. g. feasible to make the valve disk 8 integral with the push rod 4, although this is not the preferred embodiment. In such case the stem 6 with its spring 10 will best be non-integral with the valve disk.

Another structural variation consists in reversing the air valve function, i. e. letting the air valve open on its motion towards the right. This is easily accomplished by using a pulling link-rather than the push rod 4-as a motion transmission member between the cam and the valve. It should be observed that the fuel injection will in this case take place during the closing period of the air valve.

These alternative solutions of the design problems connected with the invention should be regarded as equiv alents of the embodiment previously described.

I claim:

1. A combined air intake device and fuel injection pump Number for a 2-cycle internal combustion engine utilizing volatile fuel comprising, in combination, a cam-actuated air intake valve having a valve body and cooperating valve disk, a sleeve in said valve body, a hollow stem extending from said valve disk and guided for axial movement in said sleeve, a fuel admission port in said valve body communicating with the internal bore of said sleeve, and means for injecting fuel from said port through said sleeve and said hollow valve stem into the engine crankcase as said air intake valve is actuated by its cam.

2. A device as claimed in claim l, characterized in that said injection means comprises a piston mounted in alignment with said valve stem in an enlarged bore in said sleeve, said piston cooperating with said valve stem to inject fuel into the crankcase.

3. A device as claimed in claim 2, characterized in that spring means are provided normally keeping said piston against said valve stem, said spring means yielding as pressure builds up in said large bore whereby a passageway is opened between the piston end and the hollow valve stem permitting injection of fuel through said stem.

4. A device as claimed in claim 2, characterized in that said sleeve is slidably mounted in said valve body, said inlet port moving with said sleeve, said movement of said sleeve determining the amount of fuel admitted during any stroke of said valve and further characterized in that said valve body is provided with an adjustable air intake port andmeans are provided for simultaneously regulating the position of said sleeve and said air intake port.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Baird Dec. 24, 1907 Jay Dec. 17, 1918 

